The purpose and scope of this project is subdivided in two specific aims that are detailed below: Specific Aim 1: Develop Multifunctional Liposomes with Targeting, Imaging and Drug Delivery Capabilities We are developing lipid-based nanoparticles (liposomes) bearing targeting and on-demand drug release properties for improved delivery of cancer therapeutics. For light-triggered applications, we have designed liposomes from a photopolymerizable diacetylenic phospholipid (DC8,9PC), based on its unique partitioning in the liposome membrane. Our formulations also include a tunable aqueous photo-sensitizer to promote electromagnetic radiation-triggered drug release. For biological applications (localized drug delivery), we have used a visible light source (514 nm laser) that does not affect cell viability. Pre-exposure of liposome/cell suspensions to the laser results in improved efficiency of doxorubicin delivery to cells1 (based on cytotoxicity assays). Our animal studies using the human nasopharyngeal carcinoma (KB)-Xenograft mouse model show that DPPC: DC8,9PC liposomes show similar biodistribution when compared with control (DC8,9PC minus) liposomes. We are further developing these liposomes for their drug delivery applications in vivo. To improve breast cancer treatment, we have coupled the targeting potential of HER2-specific Affibody molecules with the thermosensitive properties of liposomes (HER2+ Affisomes). We have successfully demonstrated using cell culture experiments that the HER2+ Affisomes are suitable vehicles for intracellular delivery of liposome-entrapped contents. Further development of these nanoparticles for delivery of anti-cancer agents will prove to be beneficial for breast cancer treatment. Specific Aim 2. Development of Radiation Induced and Targeted Chemotherapy (RITCH). The concept envisions a non-toxic pro-drug that when administered intravenously will distribute throughout the body. When the pro-drug is subjected to localized electromagnetic radiation it will undergo a chemical transformation into a cytotoxic compound at the site of the tumor. We have used as a prototype the hydrophobic membrane probe Iodonaphthyl-azide (INA), which upon light irradiation undergoes a covalent reaction with transmembrane portions of membrane proteins. Photo-activation of INA affects the signaling capabilities of numerous cellular receptors and results in cell death. Since the INA treatment eliminates multidrug transporter function in addition to other membrane proteins, this approach is advantageous for treatment of multidrug resistant tumors. The unique mechanism of action INA targeting membrane proteins thus provides a novel and potent chemotherapeutic approach. Recently we observed that alternate radiation modalities (e.g. sono-cavitation and X-ray radiation) can trigger the reactivity of RITCH compounds. We plan to examine efficacy of our RITCH compounds in vitro and in vivo using various modes of triggering that include light, sono-cavitation and X-ray radiation The animal studies involve pharmacokinetics, bio-distribution and toxicity using the small animal imaging facility at NCI-Frederick. We are designing new RITCH compounds that will be more amenable to various triggering modes. In addition we are pursuing basic studies on the chemistry of the new compounds as well on cell biological events that lead to apoptosis and cell death.